Telephone system



Sept. 19, 1939. E. P. G. WRIGHT TELEPHONE SYSTEM A Filed Aug. 2l, 1956 /NVENTOR E. R G. WRIGHT ATTORNEY Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE land, assigner to Western Electric Incorporated, New York,

of New York Company, N. Y., av corporation Application August 21, 1936, Serial-No. y97,113 In Great Britain October 4, 1935 21 Claims. (Cl. 179-48)V This invention relates to telephone systems and particularly to systems comprising automatic switching equipment for use in completing connections.

The object of the invention is to facilitate the establishmentl of desired connections and to otherwise increase the eciency and adaptability of automatic switching equipment in telephone systems.

A feature of the invention is a telephone system inl which a special switch is provided for use in place'of the usual switching equipment for directly connecting one of certain subscribers lines with another of these lines, vThe switch is selectively controlled by non-locking keys at the stations, a key'being provided at each'station for each of thel other lines jto which the switch gives direct access."

Another feature of vthe invention is a telephone system in' which the special switch, which is operatively controlled by a non-locking key at a subscribers station to directly connect this station with a certain other station, is released by replacing the receivers at'these stations.

` Another feature of the invention is a telephone system in whicha special switch is provided for directly interconnecting any two of certain stations, the switch being arranged to `give the calling station a busy signal if the station with which connection is desired is busy, the busy signal being terminated and the desired connection establish ed ifthe called v station becomes idle before the calling station releases-the switch.

These and other features of the invention will be more completely described by considering a telephone system in which the invention is embodied, one'` such system being illustrated in the drawing which forms a part of this specification. The invention Vis not limited in its application to the particular system shown but is, in general applicable to any manual, automatic or semi-automatic system.

Referring to the drawing, a telephone system isrepresented schematically by two subscribers stations A and B, a nderswitch LF and a start circuit SC.

The-special finder switchLF comprises an operating magnet LEM, a setvof eight brushes and an associated. bank of terminals. The brushes LFMI, LFM2, EEMB, LFM4 and LFMS are used for establishing and controlling the establishment of connections with calling stations such as B; the brushesLFME, LFMB and LFMI are used for establishing connection with a called station such as A. More than one of -the special Iinder switches LF maybe provided, the start circuit SC being arranged as shown in the drawing to controla group of four'of such switches controlled from onev or more stationsB and having access to one or more stations A. Whenassociated with a group offour' such iinder switches, the start relay ST is provided 'with three more contacts similar to st3 and three more contacts similar to std.

The station A represents one to which calls from one or more other stations may be completed by a special finder 'switch LF controlled from the calling station. The station B represents one which is provided with special non-locking keys KI, K2 for use in controlling the operation of a special finder switch LF to establish connection with a desired station to which the switch LF has direct ac'cess. A special line relay Q is provided.' for the station B shown and a similar relay is providdfor each other 'station which is arranged to' control a nder switch LF. Of course, the usual line" relay and other line circuit apparatus is provided for the line of each of these stations but is'not shown in the drawing other than being represented by the dotted lines leading to the terminals and associated set of brushes of line linder and final selector switches, which switches 'are adapted to complete regular calls to and from these lines. If the central oliice equipment is manuallycper'ated, the lines are connect-V ed to jacks atn an operato'rsp'osition instead of being connectedto the' banks of line iinder and selector switches, as shown.

' The upper springs of keys Kl, K2 at a station B are connected to the exchange by 'a common conductor, and in the exchange to the special line relay Q; so that operation of any one of the keys causes'the operation of relay Q to start one of the finders LF. The middle springs of keys Kl, K2 are connected to thel exchange by individual conductors, and in the exchange to adjacent terminals in the group accessible to brush LFMI The lower springs` of keys KI, K2 are connected to the exchange by a common conductor and in the exchange to relay DA of the start circuit SC.

The line virom each station such as B is connected to as manyY positions in theiinder switch LF as there are stations such as A to which this switch gives direct access; and in each of these positions, a connection is established from the station such as B to a different one of the stations such as A. Thus the line :of station, such as B, is connected to lfour succeeding terminals in the terminal groups to which brushes LFM3 and LFM4 have access, and the line of each station such as A is connected to a different one of the corresponding four terminals in the terminal groups to which brushes LFMS and LFMB have access. The line A is also connected to one of the terminals in each such group of four succeeding terminals to which brushes LFM5 and LFMS have access so that each of the stations such as B will have direct access to the line A. If station A is also one provided with a set of keys KI, K2, and served by the same nder or finders as is station B, then the line of station A is connected to a group of four succeeding terminals in the terminal groups to which brushes LFM3 and LFM4 have access. And if line B is also one to which the switch LF has access on calls from stations provided with the keys Kl, K2, then this `line is connected to one terminal of each group of four succeeding terminals to which brushes LFMS'and LFMS have access.

Assuming now that ithevsubscriber at station B desires a quick and vdirect connection with station A, Akey Kl fis actuated thereby momentarily closing a circuit from battery in the start circuit SC, Vthrough the winding of relay DA, both contacts of key Kl, back contact of spring q2 and winding of relay Q to ground. The special -line relay Q is operated by the current in this circuit but relay DA does not operate. The rectier MRA is poled to prevent the operation of relay Q in series with the cut-off -relay (not shown) 'to which Vit is normally connected at the back contact of. spring qd. Relay Q locks through the front contact of spring q2 and the back Contact szl of relay SZ in the start circuit. At contact Q4, relay Q connects ground over the test conductor to operate the cut-01T relay (not shown) of the regular line circuit to prevent seizure of the line on an incoming call; and, at contact ql, relay Q closes a circuit'for operating start vrelay ST. The rectiiier MRB prevents the short-circuiting of the winding of relay Q when spring 14 closes its front Contact.

At itscontact std, relay ST closes a circuit which includes contacts kl and kafl for operating the driving lmagnet LFM; at the other like contacts (not shown) of relay ST, similar cir-" cuits are closed for operating the driving magnets of other idle finders in the group. The brushes of `switch LF are thereby advanced stepby-step untilY brush LFMl finds .the terminal to which keyv KI is connected at which time a circuit is closed from ground through contact st3,

both windings of relay 'K in series, brush LFMI,

terminal to which .key Kl is connected and through the lower contact of key KIV and Winding of DA of the start circuit to battery. Relay DA is not operated but relay K is operated by the current vin this circuit. At the back contact of spring kl, the circuit for operating the magnet LFM is opened to prevent further advance of the brushes; and, at the front contact of spring kl, the left winding of relay K is short-circuited by the ground at contact std, thereby increasing the drop iny potential through the right winding of relay K suiciently toprevent seizure of the line by any of the other special finder switches which may be hunting. At contact k2, relay K closes a circuit for operating relay KA, and relay KA locks through its contact ka2, brush LFMZ, and contact g3, to ground. The key Kl having been actuated long enough for the switch LF to find the position corresponding to the calling and called stations, the calling subscriber Yreieases key Kl vand removes the receiver from the receiver hook and a circuit is closed from battery through the lower winding of relay S, contact ka 3, brush LFM3, over conductor a and through the calling station B, back over conductor b, through brush LFM4, Contact lca4, and through the upper winding of relay S to ground. Relay S operates and at its contact s4 connects ground through brush LFM8 and rectier MRA to short-circuit the winding and thus cause the release of relay Q. The release of relay Q causes the release of relay ST, thereby stopping the operation of any other line finder which was set in operation by relays Q and ST. The release of relay ST also causes the release of relay K. Relay KA remains operated under the control of Contact sl of relay S.

If station A is idle when the brushes of switch LF are advanced to one of the positions in which this line is accessible, the test relay T is operated by the current in a circuit from ground through the winding of relay T, contact s3, brush LFM1, to battery through the cut-off relay (not shown) of the line to station A. Relay T closes a circuit at its contact tl for operating relay TT. Relay TT locks through its contact ttl and contact sl; and at its contact ttSshOrt-circuits and causes the release of relay T. The operation of relay TT closes a ringing ycircuit from the ringing source, through the left winding of relay F, back contact of spring f3, contact tt, brush LFMB, over the line to station A and through the ringer (not shown) thereat, back through brush LFM5, contact ttS, and back contact of spring ,f2 to grounded battery. Relay F is marginal and does not operate until Vthe receiver is removed at station A. Ringing tone lead RTL is connected through the front contact of spring tt2 and contact fl, in parallel with the lower Winding of relay S, to conductor a of the line to station B. When the receiver is removed at station A and relay F operates, contact f4 opens the short circuit around the right winding of relay F so that relay F holds under control of contact ttB, the ringing circuit is opened at the back contacts of springs f2 and f3; and a talking circuit is closed through the windings of inductance I, the front contacts of Vsprings f2 and f3 and through brushes LFM5 and LFMB'and over the line and through the telephone at station -A. Talking battery is'supplied to station B through the windings of relay S.

' If .the called station is busy, the test terminal with which brush LFMIis engaged is at ground potential and relay T does not operate. In this case the busy-tone conductor BTL is connected through `contact s2, back contact'of spring ttZ and contact fl, to the a conductor of the line to station B in parallel with the lower winding of relay S. If, before the subscriber at station B releases theconnection, the called station becornes idle, relays T and TT are energized and the ringing circuit is closed as hereinbefore described.

If the calling subscriber does not hold the key Kl operated long enough for the line relay Q to close its locking circuit, removal of the receiver will initiate a regular connection. If the key is depressed long enough to operate and lock relay Q but the subscriber doesnot thereafter remove the receiver, a finder LF finds the marked position as hereinbefore described but relay S does not operate. In this c`ase,relay Q remains operated until its circuit is opened a predetermined interval of time after the startrelay ST is operated. To this end, relay ST connects ground switch.

from contact S22, through its contact stZ to con# ductor STL to start the operation of a common timing circuit if not already in operation. Relay ST also connects the winding of relay SA, through contact stl, the back contact of spring &2 and contact S23 to the pick-up lead SL of the timing circuit, to which lead ground is connected at the beginning of each such predetermined interval measured oi by the timing circuit. Relay SA is operated, as soon after it is connected to lead SL as this lead is connected to ground, and locks through the front contact of spring sa?. At contact sal, relay SA connects the winding of relay SZ to lead ZL, to which conductor ground is connected at the end of the desired interval as measured by the timing circuit. Relay SZ operates and, at its contact sal,

opens the holding circuit of relay Q. Relays Q,

ST, SA and SZ are thereupon releasedv in the order named.

If the subscriber at station B desires simultaneous connection with more than one of the stations to which the special line inders give access, depression of each key corresponding to a desired station causes the operation of one of the finders and connection is then established with the desired stations.

The special nder LF might be used for completing incoming calls from another exchange by providing a group of relays, or other switch, op.

erated over the interoirice trunk for controlling the special iinders as desired.

What is claimed is:

l. In a telephone system comprising subscrib-ers lines, normally-employed switching means for establishing connections between any two of said lines, and a` switch for establishing direct connections between any one of certain of said lines when calling and any desired one of certain of said lines, said switch operating only as a finder switch.

2. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections between any two of said lines, and a switch for establishing direct connections between any one of certain of said lines when calling and a particular one of said lines, said switch operating only as a iinder 3. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections betweenany two of said lines, and a switch for establishing direct connections between any one of certain of said lines and any `of other certain ones of said lines, said switch operating only as a finder switch.

4. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections between any two of said lines, and a switch for establishing-direct connections between any two of certain of said lines, said switch operating only'as a nder switch.'Y

5. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections between any two of said lines, a switch for establishing direct connections between any one of certain of said lines when calling and any desired one of certain of said lines, said switch operating only as a finder switch, and a set of keys at the subscribers station of each of said rst mentioned certain lines for controlling the operation of said nder switch, each of said sets of keys including a different key for calling each of said last mentionedv certain lines.

6. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections between any two of said lines, a switch for establishing direct connections between any one of certain of said lines when calling and a particular one of said lines, said switch operating only as a finder switch, a key at 'the subscribers station of each of said certain lines for initiating and controllingfthe operation of said finder switch to establish connection between the vcalling `one of said certain lines and said particular line;v

7. In a telephone system comprising subscribers lines, normally-employed switching means for establishing connections between any two of said lines, a switch'forestablishing direct connections between any one of certain of said linesl and any of other certainl ones of said lines, said switch operating only as ainder switch, and a set of keys at the subscribers station of each of said certain lines for controlling the operation of said nder switch, each ofsaid sets of keys including a diiTerent key for calling each of said other certain lines.

8. In a telephone system comprising sub-- scribers lines and means for establishing connections between any two of said lines, a switch having one set of brushes for connecting directly with a calling line and another set of brushes for connecting directly with a called line, certain but not all of said lines beingconnected to terminals with which the brushes of said first set can engage and certain but not all of said lines being connected` to the terminals with which the brushes of said other set can engage, said switch operating only as a finder switch.

9. In a vtelephone system comprising subn scribers lines and means yfor establishing connections between any two of saidlines, a nder switch having Vone set of brushes for connecting directly with a calling line and another set of brushes for connecting directly with a called line, eachof certain but not alllof said lines being connected to terminals'withjwhich the brushes of said rst set engage in succeeding positions of theA switch, and4 eachof certain but not all of said linesbeing connected to 'a different set of the terminals with which the brushes of `said second set engage when the brushe'sofsaid first set are Vin engagement with leach of the succeeding sets oi Y terminalsv to which eachlof said rst mentioned certain lines are connected.

110. Ina telephone systemcomprising subscribers lines and means for establishing connections between any twov of said lines, a switch having one set of brushes for connecting directly with a calling line and a secondset of brushes for connecting directly with'a called line, each of certain but not all of said lines being connected to terminals withwhich the brushes `of said rst Yset can engage-and eachof certain'but not all of .said lines being connected to terminals with which the brushes of said second set can engage, said two sets of brushes being effective in different posi tions to connect each of said first mentioned certain lines with each of said last mentioned certain lines, said switch operating only as a finder switch.

1l. In a telephone system according to claim 10, a set of keys at theV subscribers station of each of said rst mentioned certain lines for controlling the operation of said nder switch, each of said sets of keys including a dierent key for calling each of said last mentioned certain lines.

12. In a telephone system according to claim 10, a set of non-locking keys at the subscribers station of each of said first mentioned certain lines for use in initiating and controlling the operation of said finder switch, each of said sets of keys including a different key for calling each of said last mentioned certain lines.

13. In a telephone system according to claim 2, a key at the subscribers station of each of said certain lines for controlling the operation of said finder switch, and relay means controlled by the receiver hook at a calling station for completing a talking connection through the brushes of said switch between the calling station and said particular station.

14. In a telephone system according to claim 2, a set of non-locking keys at the subscribers station of each of said certain lines for controlling the operation of said nd-er switch, means responsive to the temporary operation of the key at the station of one of said certain lines for initiating and controlling the operation of said switch, and relay means co-ntrolled by the receiver hook at the calling station for testing the busy or idle condition of said particular line.

15. In a telephone system according to claim 10, a set of non-locking keys at the subscribers station of each of said first mentioned certain lines for use in initiating and controlling the operau tion of said finder switch, each of said sets of keys including a different key for calling each of said last mentioned certain lines, a supervisory relay, and means effective upon said switch being advanced to a position in which its brushes are engaged with the terminals of a calling line and the called line for connecting said supervisory relay to said calling line.

16. In atelephone system according to claim 10, a set of non-locking keys at the subscribers station of each of said iirst mentioned certain lines for use in initiating and controlling the operation of said finder switch, Veach of said sets of keys including a different key for calling each of said last mentioned certain lines and relay. means controlled by the receiver hook at a calling line for completing the connection through the brushes of said switch between said calling line and the called line.` y.

17. In a telephone Ysystem according to claim 10, a set of non-locking keys at the subscribers station of each of said rst mentioned certain lines for use in initiating and` controlling the operation of said finder switch, each ofV said sets of keys including a different key for calling each of said last mentioned certain lines, a supervisory relay, means effective uponsaid switch being advanced to a position in which its brushes are engaged with the terminals oi. a calling line and the called line for connecting said supervisory relay to said calling line, means effective upon operation of said supervisory relay over the calling line for completing a talking connection through the brushes of said switch between said calling and called lines, and means effective upon release of said supervisory relay when the calling subscriber replaces the receiver for releasing the connection between said lines.

18. In a telephone system according to claim 10, means comprising keys at each station of said rst mentioned certain lines for initiating and controlling the operation of said nder switch, a supervisory relay connected to a calling line upon advance of the switch into engagement with the terminals of a calling and a called line and controlled by the receiver hook at the calling line, and means controlled by said relay for testing the called line to determine whether it is busy or idle. Y

19. In a telepho-ne system according to claim 10, means comprising keys at each station of said first mentioned certain lines for initiating and controlling the operation of said finder switch, a supervisory relay connected to a calling line upon advance of the switch into engagement with the terminals of a calling and a called line and controlled by the receiver hook at the calling line, and means controlled by said relay for testing the called line, for ringing the called station if the called line is idle or as soon after operation of said relay as said called line becomes idle.

20. In a tel-ephone system comprising subscribers lines and means for establishing connections between any two of said lines, nder switches, each switch having one set of brushes for connecting directly with a calling line and another set of brushes for connecting with a called line, each of certain of said lines being connected to terminals with which the rst set of brushes of each of said switches can engage, and each of certain of said lines being connected to terminals with which the other set of brushes of each of said switch-es can engage, keys at each of said rst mentioned stations, a different key for each of said last mentioned certain stations with which direct connection may be desired, and means comprising the key at a calling station which identies the one of said last mentioned lines with which connection is desired for initiating the' operation of the idle ones of said iinder switches and for stopping one of said switches in a position in which its brushes are in engagement with the terminals of the calling and called'lines, the two brush vsets moving together and to the same extent to connect with the calling and called lines. i

21. In a telephone'system comprising subscribers lin-es, switching means for establishing connections between any two of said lines, and other switching means for establishing direct connections between calling and called lines, said other switching means comprising a unidirectional finder switch having two sets of brushes one set for connecting with the calling line and the other set for connecting with a called line, said switch operating solely as a nder switch.

ESMOND PHILIP GOODWIN WRIGHT. 

